This invention relates to an unbalanced hydraulic amplifier valve assembly which is particularly adapted for use in brake systems for automotive vehicles and which is of the type described in U.S. Pat. No. 4,516,470 to Warnecke et al, issued May 14, 1985, whose contents are incorporated herein by reference.
It is known that a determined fit is needed between coaxially arranged, axially relatively movable sliding elements of hydraulic valve assemblies, particularly hydraulic amplifier valve assemblies. In order to reduce the work input involved in the machining of parts to ensure such a fit, without adversely affecting the control or amplifying functions of the valve assembly, U.S. Pat. No. 4,379,423 Leineweber et al, issued on Apr. 12, 1983 discloses the provision of coaxially arranged slide elements such as an amplifier piston and a control plunger, as an unbalanced unit. By virtue of a loose fit, the control plunger may, to a certain extent--which is very small relative to its axial displaceability--move radially within the amplifier piston and the control ports in the latter are asymmetrically arranged, relative to its circumference. These known unbalanced hydraulic amplifier valve assemblies have been found to be useful in practice.
In order to eliminate, in the mobility of the above-outlined known unbalanced hydraulic valve assemblies, a certain degree of tightness which is caused by ring seals provided between an amplifier piston and a control plunger received therein, the above-noted U.S. Pat. No. 4,516,470 discloses an arrangement in which the axially displaceable and radially movable control plunger is supported in the axial passage of the amplifier piston without the use of axial ring seals and the control plunger is pressed against the inner wall of the surrounding amplifier piston by a transverse piston energized by the working pressure (system pressure) of the valve assembly. The radially oriented force of the transverse piston is applied to the control plunger in the zone of a control port which is provided in the amplifier piston and which is asymmetrical relative to the circumference of the control plunger or the amplifier piston. Despite the omission of ring seals on either side of the control ports and despite the coarse (loose) fits between the control plunger and the amplifier piston, the above-outlined arrangement provides for a reliable and highly hermetic seal when the control ports are closed.